138 



THE BATH OOLITE PERIOD. 



CHAP. 



In some cases these are confined to very narrow limits, and are really 

 characteristic of definite geological epochs b . Under two principal 

 groups several subdivisions are included ; but the Fuller's-earth 

 zone is kept separate, on account of its argillaceous character. The 

 sands and cephalopoda bed are included for convenience of study. 



Oxford Clay above. 



Avicula echinata. 

 Nucula lachryma. 

 Terebr. maxillata. 



Ostrea acuminata. 



Cornbrash. Nucl. orbicularis. 



f Upper or Forest 

 marble. 



Middle or Great 

 oolite. 



Lower or Stones- Hemicidaris Stokesii. 

 field. 



Fuller's-earth. 



Lias clays below. 



Proceeding eastward from Cheltenham toward Oxford, as the 

 sections in Plate IV. shew, the whole of this series, as well as the 

 upper parts of the lias, grows thinner, so that in the country about 



b See also the sections in Plate IV. and Plate V. 



